LED modules are used, for example, for backlighting LCDs. In such cases, a plurality of individual LEDs are arranged in a plane behind the display. In this case it can be difficult to achieve sufficiently uniform backlighting. These problems of uniformity have two different causes: firstly it would be difficult to construct simultaneously thin and uniform backlighting units even if completely identical LEDs were available, since particular optical construction effort is required just to achieve this “intrinsic” uniformity; secondly the LEDs are not identical. Efforts are made to use maximally uniform, presorted LEDs (“binning”).
For reasons of measuring accuracy, but above all for reasons of otherwise “combinatorially explosive” logistics, it is not possible to set the boundaries narrow enough at the LED level when binning for the variability of LEDs of the same type. Particular problems arise when, due to sequential production processes or indeed merely due to chance, LEDs with similar deviations from the mean are used close to one another.